Variable-resistance unit



Apr. 417, 1923. 1,451,678

l 'w. J. CAMERON VARIABLE RES ISTANCE UNIT Filed May 9, 1921 Patented Apr. 17, 1923.

UNITED STATES WILL J. CAMERON, 0F CHICAGO, ILLINOIS.

VARIABLE-RESISTANCE UNIT.

Application led May 9,

T o all whom it may concer/ny Be it known that I, lVILL J CAMERON, a subject of the King of Great Britain, and citizen of the Dominion-of Canada, residing at Chicago, Cook County, Illinois, United States of America, have invented'certa-in new and useful Improvements in a Variable- Resistance Unit, of which the following is a full, clear, and exact description.

My present invention relates to a variable resistance unit, and has for its object the provision of a simple and convenient device whereby different desired amounts of resistance'may be conveniently placed in a circuit thereby altering the conductivity of the circuit and cont-rolling the action of such apparatus as it is desired to interpose in the circuit. This device may bevconveniently used, for instance, for controlling the action of an electric heating device, also for dimming an ordinary commercial incandescent bulb, or for reducing an ordinary service current so that it will be suitable for apparatus requiring less than the ordinary amount of current such as miniature incandescent bulbs..

I prefer to attain my objects in the manner and by means of the instrumentalities illustrated in the accompanying drawing 1n which,-

Figure 1 is a lon itudinal side view of a resistance unit invo ving my invention having a portion of the casing broken away for clearness.

Figure 2 is a central lon it-udinal section of the structure shown in igure 1, an incandescent bulb being shown in the socket thereof, and,

Figure 3 is a transverse section taken on line 3 3 of Figure 1.

Figure 4 is a diagram of the circuit connection.

Similar reference characters refer to similar arts throughout the several views.

T e core of my device consists of a centrally bored or centrally apertured cylinder 5 of suitable insulating material, such as porcelain, insulating composition, or built-up lor composition mica, the surface of which has a suitable coil or helix 6 imbedded therein of suitable resistance wire, and of which there are several kinds upon the market. The imbedding of the helix is secured -by proper applications of suitable insulating material after the helix is wound 1921. Serial No. 467,973.

in place .upon the original core. At the A preferably flat rod of copper 8 extendsl longitudinally of the Ycylinder 5 and is spaced therefrom and assembled therewith by means of disk-shaped centrally bored ears 9, produced laterally from each end of the rod 8 to lie over and adjacent the opposite ends of the cylinder 5. The cylinder 5 is surrounded for the greater portion of its extent with a split retic'ulated cylindrical jacket 10, the upper edge thereof extends into an annular groove 11 in the lower edge or face of an insulating cap block 12, while the lower end of the jacket 10 extends into a like annular groove 13 in an insulating socket block 14 'which is provided with a socket 15 in its opposite face. Both the cap block l2 and the socket block 14 are centrally bored at 12a and 14 so as to register with the central bore 5a in the cylinder 5, and also a central bore 16a in an insulating plug piece 16; the outer longitudinal surface whereof is lrovided with a preferably threaded shell of conducting material. if 1 A headed central bdlt 18 passes through the central bore 16a the plug piece, the bore 12a inthe cap bld'k, the bore 5n in thc cylinder, and the bere 14a in the socket block, besides the central bores in the disks or ears I9, from which however it is insulated, and with a nut 19 serves to unite and bind the above-mentioned parts together, and also to form a, central contact for the plug piece 16 and the socket 15. To secure a firmer holding of the ears 9 an intermediate nut 2O is screwed onto the bolt 18, so as to come immediately above the upper ear 9, from which it is insulated by means of the insulating washer 21.

The cap block 12 is eccentrically but lon itudinally bored at 22 for the passage oiga conductor 23 which connects the threaded shell 17 on the plug piece 16 with the ear ot' the bar 8.

The socket block 14 is also longitudinally and eccentrically bored at 24 forthe passage of a conductor 25, from the lowermost contact blocks 7 to a conducting threaded shell 26 carried in and adjacent the sides of the or bar 8 in all positions, and the other end of which may be brought by the movement ot the block 27 successively into contact with any of the contact blocks 7.

lllhile a small amount of current will always pass through the helix or coil 6 when the circuit is closed by the insertion of a suitably connected terminal plug 31 in the socket 15 the greater portion of the current will pass from the threaded shell 17 through conductor 23 to the rod or bar 8, and from thence through the bridge piece 30 to the particularcontact block 7 with which the opposite end of the bridge piece may be in contact. The current will then flow from the particular contact block 7 with which the bridge piece is in connection to the lowermost point of the coil or helix 6 through the conductor 25, threaded shell 26, plug 31 or other apparatus, back through the bolt 18 to the central contact of the plug piece 16.

It will be seen that the entire resistance element may be cut out of the circuit without detaching the unit by bringing the bridge piece 30 into contact with the lowermost of the contact elements 7.

What I claim as new is 1. A' variable resistance unit comprising a hollow insulating core,a helix of resistance metal wound thereabout, a series of spaced contact elements secured respectively to different convolutions of said helix, a' layer ot' insulating material covering said helix and all but the outer faces of said contact elements, a conductor disposed longitudinally of and spaced from said core and helix, a longitudinally slotted casing surrounding said core and conductor, an insulatingl slide mounted in the slot of said casing, and a conductor bridge carried by said slide and extending from said conductor to alinement with said series of contact elements.

2. A. variable resistance unit comprising a hollow insulating core, a helix of resistance metal wound thereabout, a series of spaced l contact elements secured respectively to different convolutions of said helix, a layer of insulating material covering said helix and all but the outer faces ot said contact elements, a conductor disposed longitudinally of and spaced from said core and helix, a.

longitudinally slotted casing surrounding said core and conductor, an insulating slide mounted in the slot of said casing, a conductor bridge carried by said slide and extending from said conductor to alinement with said series of contact elements, a centrally bored plug and socket, and a single bolt extending through the b ores of said elements and constituting one element of a circuit between an'd the central terminals of said plug and socket.

3. A variable resistance unit comprising a core of insulating material, a length of Wire of resistance material Vcoiled aro-und said core, a series of spaced contact elements secured to spaced convolutions of said wire` a layer of insulating material covering said core and ,coils and exposing the outer faces of said contact elements, a straight conductor extending parallel with said core, a movable bridge one portion thereof constantly engages said straight conductor and the opposite portion is adapted to successively contact said contact elements, and means for slidably mounting said bridge.

4. A variable resistance unit comprising an insulating core, a resistance coil around said core, a plurality of spaced contacts engaging respective portions of said coil, a conductor extending longitudinally of said core and spaced from said coil, a movable bridge engaging said conductor and successively engaging said contacts, a conductor extending longitudinally through said core and beyond the ends thereof, plug and socket shells spaced from the ends of saidy central conductor, and circuit conductors respectively connecting one of said shells to said coil and the other of said shells to said spaced conductor.

5. A variable resistance unit comprising a core of insulating material, a conductor'disposed longitudinally of and spaced from said core, a resistance coil around said core. a bridge movable longitudinally upon said conductor and successively engaging convolutions of said coil, and `,plug and socket members disposed at opposite ends of said core, said plug and socket members respectively connected with said coil and said conductor and having independent electrical connection lbetween the same.

Signed at Chicago, county of Cook and State of Illinois, this 3d day of May 1921.

WlLL J. CERON. 

